Lapping compound



July 12, 1960 l.. R. ALLEN ET AL 2,944,880

LAPPING COMPOUND Filed April 25, 1957 2 Sheets-Sheet 1 INVENTORS LLY R. ALLE# DUDLEY H. WOOD/4R0 BY d@ if A ORNEYS July 12, 1960 1 R. ALLEN ETAL 2,944,880

LAPPING COMPOUND Filed April 25, 1957 2 Sheets-Sheet 2 2,944,880 Lrnro .contro Lloyd R. Alien, Belmont, and Dudley H. Woodard, Cambridge, Mass., assignors, by mesn'e assignments, to Kenmore Research Company, Framingham, hiess., a corporation of @bio uned apr. as, 1957, ser. N0. 655,040 s crains. (ci. st soo results in non-welding of the fractured particles, both to each other and to the metal surface, thus avoiding sli-tailing.

This lapping compound is particularly characterized in that, while different grits are needed, the same lap may be usedV for lapping ail the way down to the desired surface huish. It is not necessary to have a series of laps, each of which laps to a particular finish.

This particular lapping compound employs abrasive particles which are characterized by a high 'melting point, and by their low coeiiicient of thermal expansion which provides for better shock resistance, and further bytheir imperfect cleavage characterized by conchoidal fractures which provide for better cutting action and longer abrasive life.

The zirconium silicate in this lapping compound has a higher modulus of rupture and a higher crushing strength and, as well, -is a( relatively hard material with a high density, which contributes to-a high heat capacity. The abrasive materials in Vthis lapping 'compound are chemically inert up to 1500" F. and more. These llapping compounds are able to produce lapped surfaces down to less than one microinch center line average.

The particular materials with which the zirconium lsilicate is used in these thixotropic gels include kerosene and hydrocarbons with a boiling point lower than`65 0 F., or lighter fractions, low viscosity hydrocarbons or synthetic esters, although it will be recognized that a low boiling point fluid, such as alcohol, 'glycols,lether, emulsions of water and alcohol or water and kerosene, may be used. It is desirable to note that the gel used must have at least a minimal lubricating ability, which may be increased by deliberate additions of extreme pressure additives. The flneness vof the abrasive particleused in connection with these rlapping compounds is in the range of 80 grit to less than l micron.

An object of this invention is to produce a new and improved lapping compound using zirconium silicate of improved lapping performance' and reduced squeeze-out between the lap and the lapped surface.

Another object of this invention is 'to producea new and improved lapping compound in which the abrasive particles do not Vsettle out and pack. This is due tothe gel structure. i

'A further object of this invention is to provide a-new 'and improved lapping compound using a single -lap4 over a Wider range of surface finishes.

94,880 Patented Juiy l2, i950 iCC Another object of this invention is to produce a lapped surface in which there is a minimum of iish-tailing caused by the welding to the surface of particles abraded out by the lapping action. This is the result of the action of the extreme pressure additive in coating each particle.

Another object of this invention is to produce a laping compound which will produce a cratered surface, which is preferred for lubrication purposes, as distinguished from a scratched surface.

Another object of this invention is to produce a new and improved lapping compound incorporating a thixotropic gel and zirconium silicate abrasive with a reduced rate of breakdown of the particles and a uniform crater depth on the lapped surface.

To the accomplishment of the foregoing and related ends, said invention then consists of the means hereinafter fully described and particularly pointed out in the claims, the following description setting forth in detail one approved means of carrying out the invention, such disclosed means, however, constituting but one of the various ways in which the principles of the invention may be used.

vThis application involves a thixotropic gelling material, such as an organophilic bentonite, and an example of these materials is dimethyldioctadecyl ammonium bentonite, sometimes hereinafter referred to as Bentone 34. This application is not limited to this particular gelling agent. The gelling agent would be employed over the entire range from l to 2() percent of the compound, and examples of the compositions `are' 4 to 5 percent ofthe gelling agent, the balance being substantially a low boiling point iluid, as above defined, such as kerosene. These materials would be properly homogenized and between 5 and 40 percent of the total weight of uid would be zirconium silicate. Generally `this would be limited to l0 to 30 percent, and 20 percent by weight of the fluid is shown -as used in the examples.

The lapping compounds would consist of a suspending medium of a mixture of kerosene and possibly a low yiscosity lubricating oil, such as 40 to'60 SUS at 75 F. This 'would be used Yand substituted into the vehicle, Le., kerosene, to the extent of 20 to 70 percent, usually 40 to 60 percent, and examples are cited below of 50 percent oil and 50 percent kerosene. That is to say, We take the vehicle or liquid of kerosene and oil and gel this with 4 to 5 percent of modied organophilic bentonite and add 20 percent zirconium silicate, the balance being lgelled kerosene and oil. In addition to this lapping compound, particularly below 1000 mesh, V5 percent of an extreme pressure additive, examples of which are given later, would `be used to prevent galling. These 'extreme pressure additivesA may be used from 1A to 20 percent, but the Vpreferred range is usually from 2 to 10 percent, and examples of 4 and 5 percent are cited subsequently.

lOne other particular advantage of :these thixotropic gels with zirconiumsilicate is thatthey are `non-melting and do not run out between the lap and the lapped surface. Also, low boiling point materials are used yto lower the surface temperature as these materials `-are boiled at the asperite point and thereby `reduce the Ytern'- perature by virtue of aphase change.

Imn the drawings:

Fig. l in the drawings is a lapped surface finish, 2,000,000ths of an inch R.M.S., taken 'at 250 power, enlarged to A500 power; and` Fig. A2`is an example of the prior art of aVan Keuren gauge block surface finish, 2,000,000ths R.M.S., taken at 250 power, enlarged to 500 power.

These drawings show that there is a cavitation produced in Fig. 1, whereas in Fig. 2 there are `a 4series of scratch marks. This is because there is a -rollingjaction which uses only the corner of the Yparticle and the rate of breakdown will be less than in the case where the tool point must carry higher loads, as in the case of the embedded particle. Subsections of Fig. l will actually show a series of indentations where a particle has been rolled.

For a clearer understanding of this action, it should be explained that a gel is a lattice work somewhat similar to a sponge in which platelets of the gelling agent are bonded to the suspending medium and to the zirconium silicate by true electrostatic forces. The thixotropic gel liquifies readily upon agitation to a fluid suspension of relatively low viscosity, and the gel reforms reversibly on standing. This has a particular desirability in that the abrasive compounds do not settle out, nor do they fall readily from vertical or slanted surfaces, as they may in low viscosity liquids, such as oils and the like.

The electrostatic forces mentioned above differ from the normal chemical forces, i.e., electrons, in their motion and set up electrostatic fields. It is the attraction of these fields, rather than the actual chemical bond due to the exchange action of the electrons, that forms the gel. This means that when the binding forces are easily broken by the application of a mechanical force, the order of magnitude of the mechanical force necessary to break an electrostatic bond is much less than that necessary to break a chemical bond. These gels are then thixotropic when they, by themselves or upon the application of a small amount of shear force, remain stationary, i.e., there is no ow. If successive shear forces are applied, as by shaking, the gel breaks down and any particles therein can be freely moved.

We have found that this combination results in a lower temperature of the lap and lapped surface. The lower temperature increases the ease of fracture of particles gouged out by the rolling action. In tests which are indeed rough, thermocouples have been placed in the back of a gauge block being lapped and tests were run on the macro-temperature, realizing that this is not the temperature of the asperite, but macro-temperatures. The results were quite definite. Thixotropic gelled abrasives ran at lower macro-temperatures than high viscosity oils or greases normally used as lapping bases.

In comparison, it can be realized that greases might be used to suspend the abrasive. These, however, provide excessive lubrication between the lap and the work piece and present rapid cutting.

At the present time when abrasives are placed in a fluid in a lapping compound that is extremely low in viscosity,

the compound is defective in that the abrasives of the substance settle to the bottom of the container within a relatively short time. It is extremely dicult to again mix the abrasive particles uniformly in the suspending medium once they have settled. This is so because vthe heavy particles settle rst and, when the cake at the bottom of the settled suspension is agitated, there is no uniformity in the mixture. By developing a gel that will keep large abrasive particles from settling appreciably, we have solved, among others, the problem of shelf life.

In the alternative, if the compounder attempts to solve the problem of settling by the use of high viscosity greases or soaps, it has been found that excessive lubrication is provided between the lap and the material being lapped and, as a result, it has been found that there is a reduction in the cutting eiiiciency of the abrasive.

In cases where the gel is non-melting, this characteristic prevents the lubricant from flowing from between the surfaces.

An object of this invention is to use a low melting point fluid, such as kerosene, esters, glycols, or any of the other materials mentioned hereinabove, as a base in the compound so as to lower the temperature at the point of fracture of the chip.

Past experience has shown that fracture is desirable, rather than smearing or asperite tearing, for metal removal. Consequently, kerosene or oils with a low boiling point were used as the most desirable medium since the use of the material tended to carry the heat away. This invention then employs a lapping fluid of kerosene or equivalent materials, preferably below a boiling point of 650 F. in which zirconium silicate is suspended with an organophilic bentonite. This is a gelling agent which prevents rapid evaporation of kerosene with the resultant drying out between the surfaces. At the same time the kerosene, because of its relatively high evaporation rate, cools the work piece and reduces the smearing action. This results in a lower macro-temperature to the gauge block or lapped piece. In place of kerosene or low molecular weight hydrocarbons, we may use alcohol, ether or water, and emulsions of water and alcohol and water and kerosene.

In connection with the compounding of these lapping compounds, zirconium silicate has been found to be effective for the following reasons. lts melting point of 2550 C. is about 500 above that of the more common abrasive materials, particularly those used in connection with lapping compounds. The melting point of another abrasive, such as corundum or aluminum oxide, is 2050 C. Zirconium silicate is a material with a higher melting point and wears better than those with lower melting points. This a denite advantage since in the wear phenomena, the temperature of certain portions, known as the asperites, becomes quite high. Bowden and Tabor have shown that when two materials with different melting points are abraded against each other, the one with the lower melting point wears faster. In general, a further characteristic of zirconium silicate which makes it very desirable in a lapping compound is that it has a lower coeiiicient of thermal expansion, i.e., 4x10*6 inches per inch per degree centigrade, as compared-with 99 percent alumina, which has a coecient of linear expansion of 8X106 inches per inch per degree centigrade. This gives zirconium silicate a better thermal shock resistance.

In connection with the fracture, zirconium silicate is known as having a conchoidal fracture. The shear stress Ynecessary to cause this fracture is higher in zirconium silicate than in aluminum oxide. This results in zirconium silicate not breaking down as rapidly and, when it does lbreak down, it breaks into irregular shapes, which have very good abrasive characteristics. A consequence of this is that to produce a certain ineness of finish, it is necessary to start with a finer grit size than would be the -case with other abrasive materials. With aluminum oxide or silicon carbide, a coarse size breaks down rapidly. If one started with the same size of zirconium silicate, one would end up with a rougher finish than with aluminum oxide of originally the same grit size.

Further characteristics that aid in its capacity as an irnproved lapping compound are that the modulus of rupture of the fine grains of zirconium silicate is 7,100 to 9,300 pounds per square inch, and its crushing strength is 41,500 to 44,600 pounds per square inch. Its hardness is about 7.5 Mohs scale and its density, which is 4.65 as compared with other abrasives such as aluminum oxide, which is 3.5 to 4.0, gives it a great heat capacity.

Furthermore, zirconium silicate is chemically inert up to 1500 C. It resists wetting under these conditions better than other materials. Since the point temperature of an asperite frequently reaches its melting temperature, and thus the temperature of the particles of zirconium silicate reach this point, it is appreciated that the resistance to fracture and the chemical inertness of the material is important, particularly at high temperatures. This chemical inertness may be expressed as being characterized by non-welding at the melting point of the asperite in an operation such as lapping. The reaction between zirconium silicate and molten steel is less than that of aluminum oxide and steel.

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coarse Work for cutting and rough nShing. Another particular size is400 mesh or 33 microns. .For slightly n'er inishes a 600 to 800 mesh may beV employed and for finest finishes perhaps 800 ltov 1000 grit may be employed, and this would correspond to 23 micron particles. 5 For what is known as a gauge block ne iinish, less than one micron particle size may be employed. It is in this latter range that the extreme pressure additives Would be used to prevent galling. To give a comparable operation, itwill be seen, comparing with the above, that in connection with aluminum oxidel 800 grit, corresponding to 18.5 micron particle size, would be employed. From the above comparison, it will be seen that one must start with a larger particle of aluminum oxide to produce the Vsame type of iine iinish because the particles cleave and break down rapidly into smaller particle sizes.

A further characteristic is that the zirconium silicate differs from other abrasives,` such as aluminum oxide or magnesium oxide and a number of the carbide abrasives, in that all of these materials will readily combine with 2O an acid slag, such Ias may be formed during an abrading operation due to the high temperature generated at the asperite points. Zirconium silicate, however, is acidic and can be combined only with great diculty with such acid slags.

Another characteristic might be its thermal expansion, which is 4.5 for zirconium silicate, whereas aluminum oxide is 8.5. By thermal expansion is meant the mean reversible thermal expansion per degree centigrade times l0-6 at a range from 20 to 1000 C. (68 to 1832 F.). With high thermal expansion there would be an increased opportunity to fracture because of thermal stress.

One of its important characteristics is that zirconium silicate does not undergo a phase changewithin the working temperature range, i.e.,=there is no brittle phase tand no temperature where vits Ashear strength undergoes a sharp drop.

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and inally settled n a npthenic oil fromrSn Oil Conipan'y Y Viscosity, SUS, 160 F. Flashpoints, 27,5 VF. Pourpoints, F. -60 units 'Firepoint, 305 F. ASTM color #2 Our present base is 50% kerosene and 50% of the above named napthenic oil plus the gelling agent, f course, as shown in the table above in the percentage indicated. Y To this we would addour I4abrasive to make it'u'p to i.e., 5-40% abrasive, generally 20% balance media, made up as above with uid and gelli'ng agent. To eliminate metal to metal galling of ferrous materials during lapping, We added to our standard base 50-50 kerosene and oil and 4% Bentone 34, with the following miniumum and maximum percent in ranges, plus the best percent:

EEP. Additive AMln., .Max., Best y Percent Percent Lard Oil M 20 10 Sulphurized Lard Oi1..-.- 3/2 10 4 Sulphurized Castor OiL-.. 10 4 Tricresyl Phosphate.. 2 l2 6 Triethyl Phosphate.. 4. 10 5 Y Chloroparaiin.. l 18 5 Lead Oleate 1 10 2 LC Basev (Ohlorinated 1 20 5 hydrocarbon) Sun Oil Company. 1...... ...d0.. LC Base (ab0ve)....` 1 20Y 10 `1 ase--50% kerosene-50% oil.V

Of these we preferred C, and H.V The one we use mostly is H; this one is suitable for making gauge blocks.

Examples Range Fluid Gelling Agent Other Components Min., Max., Pre- Percent 'Percent ferred, Percent .1 Kerosene.- Bentone 34 1..... 1 10 4% o.. 1 10 4% Oatronic SP wetting Silica Gel 1 10 4 agent. Thxcin (Baker Castor Oil). .l 10 4 Bentone 34 and Thixcin `l`l0 l-10 3/3 Attapulgns Clay.-..-.- 1 12 5 }Am1ne O Wettmg Aluminum Octoate- 1 10 3 agent.

l Dimethyldioctadecyl ammonium bentonite.

The above compositions represent the variateswe have tested on` gelling agents for kerosene.. Two more must be added for water which have proven satisfactory for Vnon-metallic lapping: Y

In general, however, no -additives `areneeded until the grit size is iner than 1000 mesh. The iiner the grit the more needed is the EP additive until for the nest lapping of gauge blocks Acomposition. I has proven useful on Range Fluid Gelling Agent, Other Components Min., Max., Pre- Percent Percent ferred,

Fercent S Water..... Bentonite l 10 4 9 Waterand d 1 10 4 ethyl alcohol.

In dealing with various ymetals it became necessary to add Vagents to the kerosene to aid in wetting and lubricity. We chose 40-60 SUS lightoilsto add. We tried -paraiinic and napthenic base oils ofthe 4same viscosity 75 the last step. Similar extreme pressure additives can be inserted for lapping compounds designed to lap nonferrous materials.

To any of the above media We have added between 5 and 40% zirconium silicate. Generally, this has been used "in the range of abrasive, 80% combined media, except for 220 grit (for finest polishing). Here we use 30 to 35% zirconium silicate, the balance being media I from the table, which` is, ofcourse, 50% oil, 50% kerosene gelled and then the extreme pressure additive of the table added. Y

These lapping compounds are made by taking a gelling agent, such as bentonite or Bentone 34, and some kerosene, land making a slurry or paste, i.e., the ingredients are first mechanically mixed and then passed through a homogenizer, such as a MantonGaulin, until the gel is formed, or until the strength of the electrostatic bond is at a maximum. Other gelling agents, such as those shown in the examples, together with saponites, zeolites, fullers earth, aryl ureas and phthalocyanine pigments, may be used. These maybe used at varying temperatures, up to the boiling point of Vthe Vorganic material used as a solvent.

We have found that there is va rolling action between the lap and the lapped surface, which causes the abrasive particles to gouge out cavities in the lapped surface. Our experience has shown that the top level of a gouged out surface, or cavitied surface, can be lowered faster by such an action than that of a surface leveled by embedded particles in a lap, as a planer machine might act.

In general, the lapping compounds above described may be used for both hand and machine lapping compounds. The Iadvantage of these compounds is thatnthey substantially reduce the time of lapping in order to accomplish a certain finish. As compared to lapping compounds suspended in oils or greases, lapping times of one-fourth of those previously needed have been produced. In other instances, in connection with a particular product, the time was reduced to one-sixth of the time ordinarily required. On` an external shaft the time was reduced to one-third, and on dies the time was Vreduced to Va fourth or fifth of the time previously needed.

A further advantage of these lapping compounds is that the lapping compounds do not work out from between the lap and the work piece due to the melting and t running of the compound. This is quite important in preventing waviness in the surface, since the oozing out of Y another area is uncovered, and, hence, again in this areav there is excessive wear. This is a source of the waviness which is normally produced in lapped surfaces. It is not to be confused with irregularities that are caused by so-called asperites, but this is a` form referred to as macro-waviness. With these new lapping compounds using our gelling agents we get a uniform metal cutting action and therefore by measurement we have a surface which exhibits considerably .reduced waviness. This action is particularly explained bythe fact that the iluid does not run outjfrom between the Alap and the work piece. The fact that the rolling particles stay between the lap and the work piece helps prevent squeeze-out. Furthermore, centrifugal force generated by rotating laps does not throw the compound of as fast if it has been gelled.

Of course, it will be appreciated that the surfacesare much easier to clean. The kerosene yand abrasive may be wiped from the surface because the abrasive is not embedded in the lap. Lapping compounds, ,of course, suspend the abrasive particles and there is reduced settling of the particles because they are embedded in a gell. Thus, all percentages given above in the examples are by weight. n A

In summary, then, the advantages of this lapping compound arcas follows: There is arminimum breakdown of the abrasiverparticles using zirconium silicate. It fractures out rather than tears out metal particles, and results in anon-welding ofthe fractured particles, Vboth to each In conventional lap-V other and to the metal surfaces, thereby avoiding lishtailing. It results in a surface finish which is unique because there is more dimensional stability. It is `better for lubrication, providing a series of cavities whch serve as pockets for theV lubricant. It is a surface where the asperite heights are more uniform than other lapping compounds, and introduces a new lapping technique wherein one may use the same lap for all :finishes from a coarse nish to an ultrafine finish. One main advantage is that a surface prepared by our technique is a better surface for lubrication since each crater serves as the origin of an oil wedge and only rounded projections are available for contact in sliding friction.

In connection with the breakdown of abrasive particles, the lapping compound does not involve the embedment of the particles inthe lap with the use of embedded particles as tool points, 4but rather involves a rolling action. The photomicrographs shown in this case show the rolling action clearly. Y

Tests using the'zirconium silicate thixotropic lapping compounds as compared with aluminumoxide Vor other materials show that the rate of breakdown of zirconium silicate is less in a thixotropic gel than that of aluminum `oxide in the same thixotropic gel by a considerable measure. These tests were performed using a definite particle size and running the abrasive for a fixed length of time on `a fixed specimen in a lapping machine. Then the media was dissolved and` Vthrough settling techniques the particle size was measured afterwards. There is no-question but that zirconium silicate breaks down at a slower ratev than other materials, as, for example, aluminum oxide. The mechanism of this Y breakdown hasbeen variously hypothesized and details o f the hypotheses-Will not be given herein. K j

A further point that was emphasized was that this new lapping compound providesfor a fracturing rather than a tearing out of metal particles. It is well known that the effect of low temperatures, as shown above, in the deformation is to increase the rate of fracture or to make the fracture amore brittle one. Tests onthe gauge blocks with a thermocouple giving the macro-temperatures bring this out clearly. It is to -be realized that these temperagel 'zirconium silicate runs at a lower temperature than the same material or other abrasives with high viscosity ons and the 1ike.

Another reason why zirconium silicate tends to frac- Ature rather than tear out, is explained by the fact that :zirconium silicate wets molten metal less than other abrasives, as, for example, aluminum oxide. The use of zirconium silicate and aluminum oxide as Crucible materials has brought this point out tometallurgists several years ago.

A third point of some importance is that we use in connection with abrasive compounds Ybelow 1000 mesh the addition of an extreme pressure additive to prevent galling. These extreme pressure additives-,form films of iron chloride, iron sulphide and iron phosphite and thus prevent pressure welding of metal surfaces.

A further distinction-invthis particular lapping compound `and technique is noted in the surface. Normal lapping technique results in a smearing of the surface, thereby leaving a non-crystalline layer which spoils on usage. Because we have a rolling action and because our particlesrform a barrier between the surface of the lap and of the piece being lapped, we do not get a smearing action but instead end up with a cut or abraded surface. Now the effect of the rolling action of many particles results in a cratered surface or a surface which resembles one obtained by shot cleaning or Sandblasting, as, for example, illustrated in connection with Fig. 1. v In the presence of a fluid film each of these craters serves as the nucleus ,of `an oil wedge. The principle of the oil wedge 'is well lknown and it is well accepted that the more oil wedges present on the surface the better the lubrication. Because the rate of breakdown of the particles is so low, an improved and more uniform crater depth is obtained. This is a surprisingly important factor in wear because a more level surface and a better wearing surface is obtained if the asperite heights are uniform.

As to the use of the same lap for all of these finishes, this new technique and new lapping compound with its rolling action puts the same finish on the lap and on the piece. That is to say, if one starts with a 300 grit abrasive, he ends up with a surface finish which has a certain crater depth. If one now goes to a finer particle size, i.e., say, grit, then the iinsh both on the lap and the lapped piece is a finer surface. The surface nish is therefore finer. Furthermore, because it is a rolling action, one'uses the corner of a larger particle to make a gouge, and, therefore, at all times the crater depth is much less than the particle size.

In the above examples, all percentages are by weight unless otherwise specified.

Having thus described the specific nature of this suspending medium for the zirconium silicate in a thixotropic gel, it will be appreciated that this invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes that come Within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

We claim:

1. A metal lapping compound consisting essentially of from l to 20 percent by weight of an organophilic gelling agent, from to 40 percent by weight of zirconium silicate particles ranging in size from 80 grit to lV micron,

and the balance from 40 to 94 percent of low boiling point kerosene hydrocarbons.

2. The lapping compound of claim l, in which from 20 to 70 percent by weight of the kerosene hydrocarbons have been replaced by a low viscosity lubricating oil.

3. The metal lapping compound of claim 1, in which from 0.25 to 20 percent of the kerosene hydrocarbons have been replaced by an extreme pressure lubricant.

4. A metal lapping compound consisting essentially of 5 to l5 percent by weight of an organophilic gelling agent,

20 to 40 percent by weight of zirconium silicate having a particle size below 1000 mesh, from 2 to 10 percent by weight of extreme pressure lubricants, and the balance 35 to 73 percent of kerosene hydrocarbons.

5. The metal lapping compound of claim 4, in which from 20 to 70 percent of the kerosene has been replaced by a lubricating oil having a viscosity of 40 to 60 SUS at 75 F.

6. The metal lapping compound of claim 4, to which up to l percent of the vehicle has been replaced by a commercial wetting agent.

7. The metal lapping compound of claim 4, in which the kerosene vehicle has been replaced by a vehicle which is a member of a group consisting of low viscosity esters, alcohols, glycols, and ethers, and mixtures thereof, having a boiling range below 650 F. and Within the range of the hydrocarbons contained in kerosene.

8. A new method of metal lapping extremely tine surfaces comprising incorporating zirconium silicate particles of a size from grit to 1 micron in an organophilic gelling agent and a low boiling point kerosene hydrocarbon together with an extreme pressure lubricant, and lapping a surface with said compound while maintaining a primary boundary lm between the lapping tool and the metal surface to create a rolling action of abrasive' particles against the surface being lapped.

References Cited in the ile of this patent UNITED STATES PATENTS 1,986,243 Arveson Ian. 1, 1935 2,006,162 Fuchs June 25, 1935 2,233,585 Commons Mar. 4, 1941 2,531,427 Hauser Nov. 28, 1950 2,673,146 Kuzmick Mar. 23, 1954 2,780,041 Larsen Feb. 5, 1957 

1. A METAL LAPPING COMPOUND CONSISTING ESSENTIALLY OF FROM 1 TO 20 PERCENT BY WEIGHT OF AN ORGANOPHILLIC GELLING AGENT FROM 5 TO 40 BY WEIGHT OF ZIRCONUIM SILICATE PARTICLES RANGING IN SIZE FROM 80 GRIT TO 1 MICRON, AND THE BALANCE FROM 40 TO 94 PERCENT OF LOW BOILING POINT KEROSENE HYDROCARBONS. 